The present invention relates to a clamping apparatus for a coil such as an electromagnetic coil which is adapted to clamp the coil for assembling it with an iron core.
Conventionally, a coil in the form of an electromagnetic coil such as an armature coil having a plurality of a generally U-shaped winding wires has been used for a starter motor for a vehicle. An example of such a coil is shown in FIG. 7 in which a plurality of conductive or winding wires 1 in the form of U-shaped copper wires are arranged in a side-by-slide overlapped relation with respect to each other in such a manner that they have radially inner legs 1a disposed to form an inner circle and radially outer legs 1b disposed to form an Outer circle concentric with the inner circle, as illustrated in FIG. 6. The thus pre-assembled coil is then assembled into an iron core (not shown) with their wire legs 1a, 1b inserted into corresponding coil slots formed in the iron core. In this case, upon assembly of the pre-assembled U-shaped wires, it is necessary to hold the pre-assembled U-shaped wires 1 in a precise form or at a precise position in order to allow smooth insertion of their legs 1a, 1b into the corresponding coil slots in the iron core.
To this end, a clamping apparatus has conventionally been used for firmly holding the inner and outer legs 1a, 1b of the U-shaped wires 1 at their precise locations.
Illustrated in FIG. 6 is one example of a conventional damping apparatus which includes a plurality of clamp pins 105 radially disposed in a circumferentially spaced-apart relation with respect to each other. Each of the clamp pins 105 has a conical tip portion which is adapted to be inserted from the radially outer side into adjacent inner and outer legs 1a, 1b of the U-shaped wires 1 so as to clampingly hold the inner and outer legs 1a, 1b between two adjacent conical tip portions of the clamp pins 105. In this regard,-however, the inner and outer legs 1a, 1b are merely clamped between two adjacent clamp pins 105 with a wedging action of the conical tip portions or frictional forces produced by the conical tip portions abutting against the inner and outer legs 1a, 1b of the U-shaped wires 1. Owing to this arrangement as well as other causes such as fine surface irregularities of the conical tip portion, variations in the conical angle thereof and the like, the inner and outer legs 1a, 1b of the wires 1 are not only difficult to exactly position but also liable to inadvertently displace relatively, easily, so the wire legs 1a, 1b upon insertion into the coil slots in the iron core may be subject to undesirable deformations and resultant damage. As a result smooth insertion of the wire legs 1a, 1b into the slots in the iron core becomes sometimes difficult, thus reducing assembling efficiency of the coil wires.